2-Million-Year-Old 'Mummy Trees' Reveal Harsh Climate

by Jeremy Hsu | December 16, 2010 07:17am ET

The remains of a mummified forest that lived on Ellesmere Island in Canada some 2 to 8 million years ago, when the Arctic was cooling. The remains could offer clues to how today's Arctic will respond to global warming.Credit: Joel Barker, courtesy of Ohio State University.

SAN FRANCISCO – When rangers came across mummified wood
uncovered by a melting glacier in the northernmost Arctic reaches of Canada,
they had no idea they were staring at an ancient forest dating back millions of
years. Researchers eventually found a twisted tangle of preserved trees that reflects
a harsh struggle to survive during an ancient global cooling period.

The spindly trees would have barely hung on during a time
when the Arctic
climate changed from greenhouse to icehouse, on top of enduring darkness
for half of each year. Signs of stress are evident in narrow tree rings and
undersized leaves that were preserved at the time of death – when a landslide
may have buried the trees alive. [Image of mummy leaf]

"We know the climate was really hitting the fan for
these guys," said Joel Barker, a biogeochemist at the Byrd Polar Research
Center of Ohio State University.

Barker discussed the find here at the 2010 fall meeting of
the American Geophysical Union. His group's discovery in Ellesmere Island
National Park represents the northernmost mummified forest site in Canada.

Making a tree mummy

Mummified trees end up preserved because they were dried out
– similar to how Egyptian
mummies were created. That means the 2-million-year-old tree remains can
still burn, if anyone was looking for some ancient firewood.

"I tried to dry some wood samples in a furnace,"
Barker explained. "I accidentally set the temperature too high, and they
caught fire."

Such tree mummies are unlike the petrified forests found in
other parts of the world, where mineral deposits from water slowly replace wood
with hard rock.

Several regions of the Arctic have mummified forests. But
the latest site stands out because it contains just a few hardy tree species
such as birch and spruce — a testament to the northernmost site's exposure to
the ancient changing climate.

"Species diversity elsewhere is quite high,"
Barker said. "In our site, the trees were living
right on the edge and struggling to survive."

Life on the edge

The site sits in an upper Arctic region that changed to a
scrubby, treeless landscape about 2 million years ago, and so researchers know
the mummified trees must be at least that old. There are also no signs of the
previously common Metasequoia redwood
trees that vanished in the area around 10 million years ago, which gives the
tree mummies an upper age limit.

The thawing permafrost and retreating glaciers driven by
global warming have helped reveal mummified trees in more recent times, but
many sites likely remain undiscovered in the vast Arctic wilderness.

Barker only found the latest site after being tipped off by
a park warden in 2009. He and his colleagues flew back in the summer of 2010 by
hopping from city to city, and then switched to a Twin Otter light aircraft
before heading to the site in a helicopter.

Getting up there

The researchers were racing against time, because they had a
planned field season of just two weeks. But foggy weather kept them grounded in
Nunavut, Canada, for a week, which left them with just four days by the time
they reached Ellesmere Island National Park.

They managed to gather what they considered as
representative samples of the mummified tree branches, roots and leaves, as
well as larger quantities to examine back in the lab. But they also hope to go
back with a broader group of experts and spend at least one month on-site.

Chemical and DNA analyses of the tree mummy samples is
ongoing as the researchers try to better understand the conditions at the time.
Eventually, they hope to run the story of what happened to the trees in reverse
and figure out how the Arctic environment will adapt to the warming world of
today.

"I think there's so much work that can be done here,
and we want to do that," Barker said.

Jeremy Hsu

Jeremy has written for publications such as Popular Science, Scientific American Mind and Reader's Digest Asia. He obtained his masters degree in science journalism from New York University, and completed his undergraduate education in the history and sociology of science at the University of Pennsylvania.